1. Field of the Invention
The present invention relates to a method and an apparatus for forming and gripping the front edge or beginning of a web of a replacement roll, as it is used in unwinding devices, for example, in rotary printing machines.
2. Description of the Related Art
DE 38 11 138 C2 shows a method and an arrangement for mechanically treating the end portion of rolled-up paper. In this arrangement, the replacement roll whose front edge is glued to the first web layer is clamped in the unwinding device of a paper-processing machine. Subsequently, a cutting device is placed against the outer surface of the decelerated replacement roll, and the cutting device is moved transversely in order to cut through several paper layers as waste. These layers are moved by means of air blowing pipe to a suction conveyor which grips the layers and moves them through rollers to a waste paper receiving device.
The above-described construction is expensive because it utilizes complicated mechanisms. In addition, the method of gripping several layers with a suction conveyor is not safe. The same is true for the further transport of the layers. Finally, since inevitably several layers of the replacement roll are cut through, the amount of waste paper is increased.
An arrangement in which only one layer of the replacement roll is cut is known from DE 39 18 552 A1. However, this arrangement requires a specific configuration of the end of the roll glue to the outer layer and a specific positioning of the roll. This arrangement is expensive because it requires complicated mechanisms for cutting, for positioning the roll, and for gripping the beginning of the web.